1. Technical Field
The present invention relates to a resistance generating device and a recording apparatus, and in particular, to a resistance generating device that generates a resistance with respect to rotation of a roll formed by winding a long recording medium, and a recording apparatus equipped with the same.
2. Related Art
There is an ink jet type recording apparatus that ejects liquid such as ink on a recording medium from a recording head equipped with a fine nozzle. In such a type of apparatus, the recording head is reciprocated in a predetermined main scanning direction, and on the other hand, the recording medium is moved in a transport direction perpendicular to the main scanning direction. The combination of the main scanning and the transportation allows adhering ink in any area of the recording medium.
In the recording apparatus having the structure, a reciprocal movement area in the main scanning direction is determined by the specification of the apparatus. Some of the apparatus has a main scanning width more than 1 m to allow recording a large sized image such as a poster. On the other hand, the length of the recording medium in the transport direction is not restricted by the specification of the apparatus. Accordingly, there is a recording apparatus that continuously forms an image by loading a roll formed by winding a long recording medium.
When the roll is loaded in the recording apparatus, an end of the wound recording medium is pulled out and is sequentially provided for image formation. Herein, when pulling out of the recording medium is stopped, there is a case that the roll is continued to be rotated by inertia and the recording medium is slacked. In such a case, when the recording medium is pulled out at the next time, a tensile force is unfavorably impulsively applied to the recording medium at the time when the slackness of the recording medium is eliminated.
Further, even when the recording medium is continuously pulled out, wrinkles and the like are difficult to occur when a moderate tensile force is applied to the recording medium. Consequently, there is a case that a resistance generating device is used in order to generate a tensile force to the recording medium when using a rolled recording medium.
In JP-A-06-219002, a roll support mechanism that utilizes an idling torque of a torque limiter as a rotational resistance of a roll paper is described. It is described that a back tension can be stably applied to the roll paper and idling of the roll paper can be prevented with the roll support mechanism.
Further, in JP-A-2002-187658 (hereinafter, referred to as Patent Document 1), a structure is described in which a friction flange that rotates in synchronization with a rolled medium is provided and a back tension is generated by biasing the friction flange with respect to a fixed member. Further in Patent Document 1, a structure for unlocking the back tension is also described. Herewith, the back tension can be generated as necessary.
Further, in JP-A-2004-291395, a structure is described in which a plurality of torque limiters and a roll paper holder axis are selectively combined. Herewith, an appropriate back tension can be generated in accordance with the types of the recording medium.
In this manner, when the rolled recording medium is used, a back tension can be applied to the recording medium that is pulled out from the roll by utilizing an idling torque of the torque limiter. Further, it is also know that a different back tension is generated in accordance with the types of the recording medium.
However, in the resistance generating device capable of switching the resistance to be generated, a switch mechanism or the like is formed outside the roll in the axis direction. Accordingly, when the resistance generating device having a switching function is used, it can not be avoided that the size of the recording apparatus or the like is increased in the width direction of the recording medium.